The invention relates to a filter cartridge to be mounted in a housing for the removal of combustible substances from exhaust gases, wherein the charged filter materials are regenerated by combustion of the collected combustible substances. A filter disposed for example in the exhaust system of a Diesel engine which is charged with carbon and is itself electrically conductive is heated by an electric resistance heater to a temperature above the combustion temperature of the substances to be removed. The filter cartridge has a hollow cylindrical body of fiber material which body is closed at one end by an end plate and, at the other end, by an annular plate with an opening for the passage of gas. Electric energization is by way of the two end plates which are electrically conductive. At the end of the cartridge remote from the filter body of the filter cartridge, the current supply is arranged in the filter in the clean gas area and is electrically and thermally insulated from the housing.
The invention is concerned with the self-regeneration of soot filters in the exhaust gas system of Diesel engines. EP-OS 0 244 061 discloses a method of cleaning, that is, regenerating electrically conductive filter cartridges charged with combustible substances by combustion with the aid of electric ignition, wherein the electrically conductive filter material itself is directly resistance-heated above the combustion temperature of the substances to be removed. In this method, the filter cartridges are charged from the outside, which leads to heat losses during the combustion by radial heat radiation and consequently, to an unfavorable combustion process. The electric current is supplied, that is, the contacts for the initiation of the combustion process are disposed in this case on the outside of the filter cartridge in the area of the uncleaned exhaust gas. This results in an abnormally high corrosion of the contacts and, consequently, to a relatively short life of the filter.
Another filter cartridge is known from EP-A 0 454 346, wherein a ceramic filter element, which is to some degree electrically conductive is charged from the inside and is directly heated electrically. As a result of the low electric and thermal conductivity of the materials utilized the regeneration capability, however, is very limited. Consequently, only relatively small amounts of the substances deposited on the filter can be burnt.
Based on this state-of-the-art, it is the object of the present invention to provide a novel filter cartridge for the removal of combustible substances from exhaust gases with a regeneration of the charged filter cartridge by combustion with the aid of electric ignition, which is effective with optimal combustion particularly for the regeneration of soot filters in the exhaust system of Diesel engines. The cartridge should not have the disadvantages referred to above that is it should be reliable and require little energy for the electric ignition.